Poly-n-vinyl lactam-polyethyleneimine flocculating composition

ABSTRACT

SOLIDS DISPERSED OR SUSPENDED IN AQUEOUS SYSTEMS ARE FLOCCULATED OR PRECIPITATED BY ADDING TO SAID SYSTEM A FLOCCULATING AMOUNT OF A BLEND, EITHER IN DRY FORM OR IN AN AQUEOUS SOLUTION, CONTAINING A POLYMERIC MIXTURE OF FROM 2 TO 4 PARTS BY WEIGHT OF A POLYVINYL LACTAM, E.G. POLYVINYL PYRROLIDONE, HAVING K-VALUE OF ABOUT 80 TO 140, AND 1 PART BY WEIGHT OF POLYETHYLENE IMINE HAVING A VISCOSITY OF ABOUT 20 TO 5,000 CENTIPOISES.

Sept. 10, 1974 Sedimentation Rate (FPM) J. L. AzoRLosA ETAL POLY-N-VINYLLACTAM-POLYETHYLENEIHINE FLOCCULATING COMPOSITION Filed March so, 1972PVP K-9O as additional Flocculant A r\ I (Note PVP K-9O as soleFlocculant gave a Settling RatezO FPM at all Levels from 2 to l8 PPM) \kPEI-IOOOas additional Floecyiant \J 7mm i 0 2 4 6 8 l0 l2 l4 i6 PPMFlocculant' in Addition 1o 2PPM of PEI-IOOO INVENTORS Julian L.Azo'rlosa Earl P. Williams ATTORNEY 3,835,084 POLY-N-VINYLLACTAM-POLYETHYLENEIMINE FLOCCULATIN G COMPOSITION Julian L. Azorlosa,Bakersfield, Calif., and Earl P. Williams, Pen Argyl, Pa., assignors toGAF Corporation, New York, N.Y.

Continuation-impart of abandoned application Ser. No. 834,797, June 19,1969. This application Mar. 30, 1972, Ser. No. 239,531

Int. Cl. C08f 45/24 US. Cl. 26029.6 NR Claims ABSTRACT OF THE DISCLOSURESolids dispersed or suspended in aqueous systems are flocculated orprecipitated by adding to said system a flocculating amount of a blend,either in dry form or in an aqueous solution, containing a polymericmixture of from 2 to 4 parts by weight of a polyvinyl lactam, e.g.polyvinyl pyrrolidone, having a K-value of about 80 to 140, and 1 partby weight of polyethylene imine having a viscosity of about to 5,000centipoises.

CROSS-REFERENCE TO RELATED APPLICATION The present application is acontinuation-in-part of applicants co-pending application entitledFlocculation of Suspended Solids, filed June 19, 1969, under Ser. No.834,797 now abandoned.

BACKGROUND OF THE INVENTION Field of the Invention This inventionrelates to the precipitation or flocculation of solids dispersed orsuspended in an aqueous system. In short, it relates to the flocculationor coagulation of dispersed solids from aqueous colloidal dispersions.

DESCRIPTION OF THE PRIOR ART It is known that aqueous solutions of saltsof polyethylene imine, such as the hydrochloride, acetate or sulfate,may be employed as precipitating agents of anionic dispersed phases,i.e., bodies dispersed in an aqueous phase which carry an absorbed orrelatively immobile anion such as organic anion, fatty acid anion,carboxylic or sulfonic acid anion. As an example of the latter, theremay be mentioned a latex containing about 10 percent of a syntheticcopolymer of butadiene and styrene dispersed in an aqueous phase bymeans of pentaerythritol mono.- laurate. To coagulate or flocculate thesaid latex, about 2.4 parts by weight of the hydrochloride salt ofpolyethylene imine in aqueous solution are required per 100 parts byweight of the latex.

From the foregoing amounts utilized in flocculating the latex, it isevident that such flocculation is rather expensive.

It is an object of the invention, therefore, to provide an improvedcomposition and process for the flocculation of solids suspended inaqueous systems.

It is another object of the invention to provide a composition andprocess for the flocculation of solids suspended in aqueous systems inwhich the flocculating ability of polyethylene imine is enhanced.

With these and other objects in mind, the invention is hereinafter setforth in detail, the novel features thereof being particularly pointedout in the appended claims.

SUMMARY OF THE INVENTION The flocculation of solids suspended in anaqueous phase is enhanced by the addition of a flocculating amount of anovel flocculating composition consisting essentially of a water solubleblend of from 2 to 4 parts by weight of poly-N-vinyl lactam having aK-value of from about United States Patent O "ice Patented Sept. 10,1974- to about and 1 part by weight of polyethylene imine having aviscosity in 5% aqueous solution at 25 C. of from about 20 to about5,000 centipoises. The blend can be added to the aqueous phase either indry form or as an aqueous solution.

DETAILED DESCRIPTION OF THE INVENTION We have found that a blend of from2 to 4 parts by weight of poly-N-vinyl lactam having a K-value of fromabout 80 to about 140 and 1 part by weight of polyethylene imine havinga viscosity, measured in a 5% aqueous solution at 25 C. of from about 20to about 5,000 centipoises displays a synergistic effect when employedas a flocculating agent for solids suspended in an aqueous media.

With reference to the polyvinyl lactam, preferably poly-N-vinylpyrrolidone, the K-value is a parameter denoting the molecular size ofthe polymer, as disclosed by H. Fikentscher, Cellulosechemie 13, 58(1932). As employed herein and in ordinary commercial practice, the2-value is determined by measuring the viscosity of a 1% solution of thesubject polymer in water at 25i0.05 C. and computing the relativeviscosity thereof, i.e. average flow time of said solution/average flowtime of water. The K-value, indicative of the particular polymer beinginvestigated, is computed therefrom in accordance with the formula setforth by Fikentscher.

As with other known flocculating agents, the flocculating abilty ofpolyethylene imines generally increases as the viscosity of the imineproduct is increased provided water solubility is preserved foreffectiveness in an aqueous media. It is within the scope of the presentinvention, therefore, to employ polyethylene imines having a viscosityeven in excess of the upper limit referred to above, the eifectivelimitation in the practice of the invention being the commercialavailability of the polyethylene imines of such higher viscosities. Apolyethylene imine viscosity Within the range of from about 20 to about2,000 centipoises or cps. has been found generally satisfactory, theflocculating ability of the polyethylene imine being enhancedsurprisingly by the presence of polyvinyl pyrrolidone in the synergisticflocculating composition of the present invention. Illustrative of thecommercially available polyethylene imine products that can be used inthe practice of the invention are PEI 600 and PEI 1000, formerly Montrek600 and Montrek 1000 respectively, both polyethylene imine products ofThe Dow Chemical Corporation. PEI 600 polyethylene imine, for example,has a Brookfield viscosity, in a 5% by weight aqueous solution at 25 C.,of 28 cps. PEI 1000 polyethylene imine product has a viscosity under theindicated conditions of about 1,200 cps. The higher viscositypolyethylene imine will, of course, have a longer polymer chain andhigher molecular weight than the relatively less viscous products. Withrespect to the PEI 600 product referred to above, for example, thenumber average molecular weight of this product will range from about40,000 to about 60,000, whereas said number average molecular weight,determined by gel phase chromatography, is in the range of from about50,000 to about 100,000 for the PEI 1,000 product.

In other words, the use of the recited blend gives superior flocculationto that obtained by the use of polyethylene imine alone. What issurprising is the fact that the polyvinyl lactam, e.g. polyvinylpyrrolidone, by itself has no flocculating or precipitating propertywith respect to suspended or dispersed inorganic or organic materials.

However, when the polyvinyl pyrrolidone or other poly- N-vinyl lactam isblended with polyethylene imine in the aforestated ratios, the resultingblend displays a definite synergistic effect. Moreover, as will be shownhereinafter with respect to the blends of polyvinyl pyrrolidone andpolyethylene imine and the use of polyethylene imine alone, whencompared on an equivalent total weight basis, the amount of polyethyleneimine is the blend is /3 to /s that of the polyethylene imine as thesole fiocculant, that is, a given amount of polyethylene imine blendedwith polyvinyl lactam, which by itself is not a flocculating agent,yields a flocculating or precipitating equivalent or superior to manytimes that amount of polyethylene imine employed without polyvinylpyrrolidone or other said lactam.

The polyvinyl pyrrolidone employed in the blend will hereinafter for thesake of brevity be referred to as PVP and the polyethylene imine willhereinafter be referred to for the sake of brevity as PEI. The blend isreadily prepared by uniformly mixing aqueous solutions of the polymericmaterials at room temperature in the aforestated ratios. For thispurpose, aqueous solutions having from about 0.02% to about by weight ofthe recited blend of PVP, or other said polyvinyl lactam, and PEI can beprepared, with a blend concentration of about 0.05% by weight beingcommonly employed, based on the total weight of said aqueous solution.Dried PVP and PEI in the desired ratios may also be blended and used assuch as the flocculating agent or dissolved subsequently to give a finalsolution which may, in turn, be used as the fiocculating agent. Theamount of the dry blend of PVP and PEI in the aforestated ratios, or thevolume of the aqueous solution blend that is employed as theflocculan't, may range from 1 to 50 or more parts per million offlocculating agent on the aqueous system containing dispersed materials,whether inorganic or organic, that are to be precipitated orflocculated. The fiocculating agents prepared in accordance with thepresent invention may be employed in the flocculation or anioniccolloidal dispersions in aqueous systems. They are excellent forprecipitating anionic dispersed latices natural and synthetic, sewagefor separating sewer sludges, for separating sludges from industrialoperations, and in its precipitation of colloidal dispersions of alltypes having an anionic charge. They are of particular interest in manyareas of mineral ore recovery.

The following examples will illustrate how the flocculating compositionis employed as fiocculant of suspended solids. In the following examplesand tables, the ratio of PVP to PEI in the blend is given, together withthe K-value of the PVP. The polyethylene imines employed in the examplesare either Dow PEI 600, formerly Montrelc 600, or Dow PEI 1000, formerlyMontrek 1000, having the viscosities indicated above and thecorresponding molecular weight ranges as also set forth above and asreferred to in the following examples.

EXAMPLE I TABLE 1 Clarification Blended flocculant: average 3/1 PVPK-90/PEI 4.00 2/1 PVP K-130/PEI 3.83 3/1 PVP K-130/PEI 3.83 4/1 PVPK-l30/PEI 3.67 4/1 PVP K-90/PEI 3.67 PEI alone 3.67 2/1 PVP K-90/PEI3.50 PVP alone 0.0

The data in Table 1 show that certain blends of PVP/ PEI give superiorclarification to that obtained with PEI alone. The fact that PVP alonehas no clarifying power indicates a definite synergistic effect betweenPVP and PEI. It should be further noted that since the blends and PEIalone were compared on an equivalent total weight basis, the amount ofPEI in the blend is /3 to /5 that of the PEI as the sole flocculant.That is, a given amount of PEI blended with PVP (which in itself is nota flocculant) will give a clarification equivalent or superior to manytimes that amount of PEI used Without PVP.

EXAMPLE II A 5% dispersion of 325 mesh amorphous silica was treated withvarious ratios of PVP to PEI. In all cases, the amount of PEI was keptconstant at 2 ppm. Sedimentation rate in feet per minute was determined.As controls, similar runs were made using only PEI and only PVP. Resultsare presented graphically in the accompanying drawing.

By reference to the drawing and an inspection of the graph, it will benoted that (1) PVP alone is not a flocculant for silica, (2) PEI aloneis a fiocculant for silica; however, the rate of flocculation is aninverse function of flocculant level, and (3) combinations of PVP andPEI produce a sedimentation rate higher than that of the PEI constituentof the blend and much higher than that obtained with a level of PEIequal to that of the total blend.

EXAMPLE III Two hundred ml. of raw sewage were measured out into a 250ml. beaker. The desired amount of fiocculant was added as a 0.05%solution. The mixture was agitated for one minute. Quality offlocculation was noted as being good using 50 ppm. of 3/1 pvp K-/PEIwherein the PEI has an average molecular weight of 40-60,000.

The flocculating compositions of the present invention are excellentflocculants for taconite tailings. Taconite ore is composed ofapproximately 25% magnetite Fe O with the remainder being quartz. Thetaconite ore is converted into a concentrate suitable for chargingdirectly into a steel furnace. Basically the concentration of taconiteore consists of blasting the hard ore rock, crushing it to suitable sizeand hauling it to the treating plant. The rock is charged with water torod and ball mills and ground to 325+ mesh size to form a slurry. Theslurry is passed through a series of magnetic separators called cobbers,roughers, cleaners and finishers. Additional water is added at eachstep, since each additional step requires a thinner slurry. Thetailings, i.e., those particles in the slurry containing less than 5percent magnetite, are drained 01f from each separation and sent to theflocculation tanks for Water recovery.

EXAMPLE IV In segments of the mining industry clarity of eflluent, whileimportant, is less important than the rate of settling and the degree offinal compacting of the sediment. Here the process may be defined as aperiod of initial settling followed by a period of compacting. Aquantity of liquid tailing at 5% solids from the taconite iron oreenrichment process were made available for testing.

Three and one-half ppm. of flocculant on solids were added in threeequal aliquots to 500 ml. of the taconite tailiugs in a graduatedcylinder. The slurry was agitated by 10 up-down strokes of a 2 /2"diameter perforated plunger. The rate and type of settling was noted asshown in the following table. Three to one ratios of PVP to PEI wereused for all mixtures.

TABLE 2 Approximate Sediment, time 1:01., after Molecular PVP PEImolecular (min- 60 minweight PVP K-value weight range utes) 1 utes 1From end of a itation to start of compacting period. 2 Montrek 1000,330w Chem. Corp. 3 Montrek 600, Dow Chem. Corp. 4 1 ppm. on tailingssolids. 5 8 p.p.m. on tailings solids.

EXAMPLE V The borax refining process entails a period of hot eX-traction of ore followed by sedimentation of insolubles andcrystallization of boraX from supernatant liquid. Here the same criteriaof maximum rate and compacting occur to an even larger degree.

Twenty-five ppm. of three to one ratio of flocculant on insolubles wereadded to 350 ml. of 5% borax ore slurried in a hot borax aqueoussolution. PEI and PVP were each employed alone and compared with acontrol (no flocculant). Following vigorous agitation, degree and rateof flocculation were noted. The results obtained are shown in thefollowing table.

TABLE 3 Sediment, 1111., after- 30 120 Clarity after Flocculant minutesminutes 120 minutes 3/1 PVP K-QO/PEI 40 Slight haze. PEI 1 68 62 0. PVPK-QO 60 Slight moderate haze. Control (no flocculant)- 110 97 Verycloudy.

Montrek 600, 40-60000 MW Dow Chemical.

BRIEF DESCRIPTION OF THE DRAWINGS The above description includedreference to the accompanying single figure drawing presentinggraphically the results of the flocculation tests as set forth inExample II.

What is claimed is:

1. A flocculating composition consisting essentially of a Water solubleblend of from 2 to 4 parts by weight of poly-N-vinyl lactam taken fromthe group consisting of polyvinyl pyrrolidone, polyvinyl piperidone andpolyvinyl caprolactam and having a K-value of from about to about 140,said K-value being determined on the basis of the viscosity of a 1%solution of said polymer in water at 25 $0.05 C., and 1 part by weightof polyethylene imine having a viscosity, measured in a 5% aqueoussolution at 25 C., of from about 20 to about 5,000 centipoises.

2. The fiocculating composition of Claim 1 in which said blend is anaqueous solution of said poly-N-vinyl lactam and polyethylene imine.

3. The composition of Claim 2 in which said blend is present in theaqueous solution in an amount within the range of from about 0.02% toabout 5% by Weight based on the total weight of said solution.

1. The composition of Claim 3 in which said poly-N- vinyl lactam ispolyvinyl pyrrolidone.

5. The composition of Claim 1 in which said poly-N- vinyl lactam ispolyvinyl pyrrolidone.

6. The composition of Claim 1 in which said poly-N- vinyl lactam ispolyvinyl piperidone.

7. The composition of Claim 1 in which said poly-N- vinyl lactam ispolyvinyl caprolactam.

8. The composition of Claim 5 in which the viscosity of saidpolyethylene imine is about 28 centipoises.

0. The composition of Claim 5 in which the viscosity of saidpolyethylene imine is about 1,200 centipoises.

10. The composition of Claim 1 in which said blend consistingessentially of about 3 parts by Weight of the poly-N-vinyl lactam andabout 1 part by weight of said polyethylene imine.

11. The composition of Claim 10 in which said poly- N-vinyl lactam ispolyvinyl pyrrolidone.

12. The composition of Claim 10 in which the poly- N-vinyl lactam ispolyvinyl piperidone.

13. The composition of Claim 10 in which the poly- N-vinyl lactam ispolyvinyl caprolactam.

14. The composition of Claim 10 in which said composition is an aqueoussolution of said blend of poly-N- vinyl lactam and polyethylene imine.

15. The composition of Claim 14 in which said blend is present in saidsolution in an amount within the range of from about 0.02% to about 5%by weight, based on the total weight of the aqueous solution.

References Cited UNITED STATES PATENTS 4/1962 Plitt 26029.6 HN 2/1967Hay 26047 E HAROLD D. ANDERSON, Primary Examiner U.S. Cl. X.R.

21054; 26029.6HN, 88 3L, 895

